Catalyst



Patented Apr. 23, 1946 UNITED STATES PATENT OFFlfiE 2,398,899 CATALYSTJohn W. Teter, Chicago, Ill., assignor to Sinclair Refining Company, NewYork, N. Y., a corporation of Maine No Drawing. Application May 22,1942, Serial N 0. 444,097

Claims. (Cl. 252-207) they are highly selective with respect toamination reactions. By their use in processes involving the aminationofoleflns at elevated temperause in the form of a suspension on acarrier, for

instance kieselguhr, has been suggested as a catalyst for hydrogenationreactions.

I have found cobalt and nickel to be particularly effective aminationcatalysts. However, I have discovered that the effectiveness asaminetion catalysts of suspensions of cobalt and nickel catalysts on'so-called carriers, particularly their effectiveness in selectivelypromoting the amination of olefins by ammonia at elevated temperaturesin the production of nitriles, is to a great extent dependent upon thecharacteristics of the so-called carrier.

The amination of olefins bytreatment with ammonia in the presence of acatalyst, as described in the co-pending joint application of Frank A.Apgar and the present applicant, Serial No. 289,186, filed August 9,1939, is favorably infiuenced by elevated temperatures. Unfortunately,undesirable side reactions such as cracking, polymerization andhydrogenation of the olefins are also promoted by elevated temperatures.By these undesirable side reactions the olefin reactant is dissipatedand the organic nitrogen compound yields of the process materiallyreduced.

Some of the so-called carriers upon which it has been suggested thatmetallic catalysts be suspended in the preparation of catalytic massesappear themselves to be active catalysts of cracking, hydrogenation orpolymerization eactions. Suspensions of cobalt or nickel on some ofthese carriers also appear to be active catalysts of these undesirablereactions. I have found that their presence in the amination reactionzone substantially promotes these competing-side reactions.

It i an object of the present invention to provide an improved catalysteffective in promoting amination but which will retard or at least notmaterially promote competing side reactions such as previouslymentioned.

The catalysts of my present invention combine both of these desirablecharacteristics, that 1s tures, the extent to which these objectionablecompeting reactions occur i greatly reduced.

I cannot state with certaintywhethcr the advantageous results-obtainedthrough the use of my improved catalysts in such amination processes aredue to the characteristics of the carrier per se or whether they are dueto the way in which the cobalt or nickel catalytic material is depositedthereon by reasons of the physical and chemical characteristics of thecarrier. However, I have found that cobalt or nickel catalysts similarlyprepared, except for the substitution of conventional carriers, aresubstantially less selective with respect to amination reactions thanare the improved catalysts of my present invention.

I have also found that the effectiveness and selectivity of the catalystprepared in accordance with my-present invention are substantiallyinfluenced by the concentration of the cobalt or nickel catalyticmaterial present in the catalytic mass.

Not only are my improved catalysts more selective in amination reactionsbut they possess improved characteristics with respect to retention oftheir selective catalytic properties and improved characteristics withrespect to their susceptibility to regeneration and to pelleting andtheir ability to withstand conditions of use and regeneration withoutobjectionable crushing or disintegration of the pelleted mass.

The various materials which have previously been used or suggested ascarriers for catalysts differ widely as to their physical and chemicalproperties. Generally, their value ha been attributed to.their extensivesurface areas.

From my comprehensive research concernin the use in amination reactionsof metallic catalysts suspended on various carriers, it appears that theeffectiveness of such catalytic masses is largely dependent upon somecorrelation of pro erties of the metallic catalyst and of'the carrier,not fully understood. The complexity of the problem is apparent when itis appreciated that, in addition to surface areas and chemicalcomposition, these carriers differ as to crystalline structure, particlesize, shape, densities, porosity and the size, shape and type of theircavities.

I have found that the use of carriers characterized by maximum surfaceareas does not necessarily result in most effective amination catalysts.The surface area of composite catalytic masses comprising cobalt ornickel suspended on a carrier is often much greater than the surfacearea of the carrier itself, butappears to depend somewhat upon thesurface area of the carrier. However, Ihave found that a compositecatalytic mass comprising cobalt or nickel and having maximum surfacearea is not necessarily the most effective in amination reactions. Thecomposite catalytic mass should be so constituted as to minimize thecompeting reactions while exerting maximum amination activity. Theimproved selectivity of the catalysts of my present invention appears.toresult from a unique combination of the characteristics of the metalliccatalysts and of the carrier.

Since catalytic masses of the type described become less active after aperiod of use and require regeneration to restore their activity, thesusceptibility of such catalysts. to regenerative treatment is of majorpractical importance. I have found that the susceptibility of suchcatalytic masses to regeneration also depends to a considerable extentupon the characteristics of the carrier.

The material which I use as the carrier or su port for the nickel orcobalt catalysts, in accordance with my present invention, is anespecially treated bentonite clay. This material is prepared bymodifying natural bentonite by treatment with sulfuric acid andthereafter subjecting the acidtreated bentonite to a severeheat-treatment. Typical of such acid-treated bentonite which I have usedwith advantage is that currently marketed under the tradenamesuper-Filtrol," by

the Filtrol Companyof California, and shown by chemical analysis to havethe following composition by weight:

The particle size of this acid-treated clay was asfollows:

I Mesh size:

60'and less. 0.00 60-100 0.10 100-200 14.34 200-300 13.82 300 up 69.33

I have found such acid-treated bentonite to have a surface area of about35 square meters per gram, as determined by the method, hereinafterdescribed. Its bulk density is usually approximately 35.25 lbs./cu. ft.If this acid-treated bentonite be used without further treatment as thecarrier for cobalt or nickel catalytic material in the preparation of acatalytic mass for use in amination reactions, the resultant catalyticmass will be found to have excessive cracki d polymerization activity.Before using this acidtreated bentonite as the carrier in accordancewith my invention, I subject it to a severe heattreatment. Thisheat-treatment consists in heating the acid-treated bentonite toatemperature of about 1400 F.-1600 F. in a mullie furnace and holding itat this temperature for a period of about 8 hours. By this severeheat-treatment of screen before use.

the acid-treated bentonite, the activity of the catalytic mass preparedtherewith in promotin cracking and polymerization is minimized. Forexample, the cracking activity of the catalytic mass prepared with theun-heat-treated clay has been found to be about 35% of that of aparticular standard. By the preliminary heat-treatment -of the clay, thecracking activity of the catalytic mass, on the same basis, is reducedto only about 5%.

During this heat-treatment, some agglomeration frequently occurs. It istherefore desirable to pass the heat-treated clay through a. 90 mesh Bythis preliminary heattreatment, the surface area of the clay has beenfound to be reduced to approximately 20 square meters per gram.

The. catalytic mass of my present invention. comprising cobalt, may withadvantage be prepared as follows: A previously filtered aqueous solutionof cobalt acetate tetrahydrate is thoroughly mixed with the clay,previously heattreated as above described. An aqueous solution of aprecipitant, for instance sodium carbonate. is then added. This sodiumcarbonate solution is added slowly, preferably in substantially equalparts with to 1 hour stirring between additions.

The final addition of the-precipitantmay with advantage be followed by 2to 3 hours stirring aftenwhich the mass is allowed to settle overnightand is thereafter washed. The washing is advantageously effected bymeans of combined decantation and filtration,- using distilled water,and is continued until only a trace of sodium ion appears in the washwater. The washed catalyst is then dried for 24 hours or longer in asteam chest. It is then ground, screened to about 8 mesh or upward andcalcined at a, temperature of 550 F. for about 24 hours in order todecompose the basic metal carbonates, produced by the precipitation. The.resulting product consists primarily of cobalt oxide supported by theclay plus a small amount of water of hydration and undecomposedcarbonates.

The suspended cobalt compound is then reduced by passing hydrogen incontact with the mass at a temperature of 650-750 F. for a period ofabout 12 hours The catalytic mass may with advantage be pelleted priorto the reduction. If desired, a pelleting agent may be used to increasethe crushing strength of the resultant pellet. However, the material maybe pelleted without the aid of a binder.

The proportions of the metal salt and-of the precipitant used willdepend upon the desired concentration of the metallic catalyst withrespect to the carrier. For example, in the preparation of a catalyst,in accordance with my invention, containing about 43% cobalt,-4240'grams (l7 mols) of cobalt acetate tetrahydrate is dissolved in 10gallons of distilled water and the solution filtered to remove anyinsoluble residue. 1000 grams of the heat-treated clay is then added tothe cobalt solution and the mixture vigorously stirred for about anhour. 2200 grams (20.8 mols) of anhydrous sodium carbonate, dissolved in4 gallons of distilled water, is then added as a precipitant, at such arate that about half of the carbonate solution is added over the courseof 1 hour, the solution stirred fora half hour and the remainingcarbonate solutionadded in asimtlar manner. The resultant catalytic massis then stirred foran hour or so longer'and allowed to stand overnightbefore washing.

water not in excess of ing method using in accordance with The catalystis thereafter washed, for instance, by -a filtration and stirringprocess. The thin slurry may be filtered and the filtercake reslurriedin gallons of distilled water, the slurry refiltered and so on until-thesodium content of the catalyst has been reduced to a satisfactory level.A concentration of sodium in the wash 1 milligram per liter, when 10gallons of wash water is used, is deemed satisfactory.

The wet catalyst is then placed in a steam chest and dried at atemperature of 250 F. for about 24 hours. The dried catalyst is thenbroken up into small lumps and calcined for about 24. hours at atemperature of 620 F. It is then ground and screened to pass a 30 meshscreen and, if desired, may be pelleted prior to reduction withhydrogen.

This material may readily be'pelleted in the conventional manner withoutthe use of a binder. However, where pellets of greater crushing strengthare desired, binders may be used without substantial loss in theselective amination activityof the catalyst. For. example, I haveobtained very satisfactory results by the followrosin as a binder:

3% of a rosin of a particle size which will pass a 50 mesh screen, isintimately admixed with the finely divided catalyst by tumbling andstirring. The powdered material is then pelleted to Iorm thin, hardpellets which are subsequently ground and screened. The resulting finegranular material, of a particle size between 30 and 50 mesh, is thenrepelleted, ground and screened as before. To the resultant granularmaterial there is added an additional amount of rosin, for example about1%, and the mixture repelleted.

These pellets are then dried in a stream of nitrogen for about 16 hoursat a temperature of 700 F. The apparent density of the dried pelletsprepared in this manner has been found to be about 1.25 gramsper cubiccentimeter and their crushing strength has been found to range fromabout 7 to about 23.5 pounds with an average crushing value of about13.5 pounds.

After the drying operation the pellets may be reduced by treatment withhydrogen as previously indicated.

I have also obtained pellets of excellent characteristics and goodcrushing strength by substituting for the above-mentioned rosin powderabout 4% starch and about 2% stearic acid as pelleting agents. Pelletsprepared in this manher have been subjected to over 100 hours of usewithout evidenceof disintegration.

The nickel catalyst of my invention may be prepared substantially asdescribed above by substituting' for the cobalt acetate a soluble nickelsalt, for instance nickel nitrate hexahydrate. However, in preparing thenickel catalyst the calcining operation should be carried on at atemperature of about 660 F.

The concentrations of the metal catalyst in the composite catalytic massmay be varied over a considerable range but I have found concentrationsof approximately 40 to 50% by weight to be most advantageous.

Generally, I have found my cobalt catalyst to be a more efiectiveamination catalyst than my v nickel catalyst of equal concentration. Inmost hydrogenation reactions, nickel has been found to be more activethan cobalt. However, in pilot plant operationa the nickel catalystprepared the present invention has been found to effect only about 90%as much total of my invention to organic nitrogen fixation as my cobaltcatalyst of equal concentration. Also, when the nickel catalyst is used,there is a greater amount of cracking than occurs when the cobaltcatalyst is used under similar operating conditions. Though lesseffective than cobalt as an amination catalyst, I have found the nickelcatalyst be far superior as an aminat io'n catalyst to catalytic massescomprising other reducible metals previously found effective ashydrogenation catalysts.

From these facts it is apparent that the ability of a catalyst toactivate the N-H bond of ammonia is entirely unpredictable on the basisof the ability of such catalyst to activate the H-H bond of molecularhydrogen for hydrogenation. The two are not equivalent nor should theybe expected to be equivalent when the differences in bond distance anddissociation energy of the NI-I bond and the H--.H bond are considered.

For the purposes of further illustrating the importance of thecharacteristics of the carrier used in the preparation of aminationcatalysts, I have tabulated below amination activities of varioussimilarly prepared catalytic masses comprising approximately 50% cobaltsuspended on various carriers. These activity values represent totalorganic nitrogen fixation, calculated as laurylamine, obtained byreacting ammonia with dodecene at .a temperature of 550 F., and apressure of 2000 pounds per square inch in the presence of cobaltcatalysts prepared with the carriers indicated, other conditions beingcomparable. Under these specified conditions the cobalt catalyst of mypresent. invention has an amination activity of about 12.

Amination Gamer activity Puinlce Kieselguhr (ordinary type) "Alumina.

Firebrick Iron oxide. I Aluminum fluoride Aluminum si In addition totheir superior amination activity, the catalysisof my present inventionare superior to those prepared with the conventional carriers withrespect to their activities in promoting competing reactions.

The efiectiveness of my improved catalysts in amination reactions willbe illustrated by the following speciflc examples of their use. In eachinstance the carrier was the heat-treated acidmodiiied bentonitepreviously described and the composite catalyst was prepared by themethod heretofore related. The catalytic activity values were obtainedin each instance from operations in which ammonia was reacted withpropylene at a temperature of 700 F., and a pressure of 3000 pounds persquare inch, and are expressed as the percentages of total organicnitrogen fixation calculated as propionitrile.

Example I In this run the catalyst used was a 41% (by iace area of thecomposite pelleted catalyst, after reduction, was 23.4 square meters pergram. The porosity of the pelleted catalyst expressed in In this run thecatalyst was a 48.5% (by weight) suspension of cobalt, in the reducedform.

, was 11.5% and the.

I aseaaee volume percent was 59.3 and the average crushing on the sameheat-treated clay carrier, pelleted by the addition of 4% rosin. Thesurface area of the pelleted catalyst after reduction was 32.8 squaremeters per gram. The porosity of the pelleted catalyst was 50.6 and itsaverage crushing strength of the un'reduced pellets was 13.5 pounds.compounds produced was 17% and the ratio of non-nitrogenous polymer tonitrogen compound was 0.32.

Example III In this run a nickel catalyst was used comprising 46.1%nickel (by weight) suspended on the carrier previously described. Thecatalyst was used in pelleted form, no binder having been employed.Thesurface area of the reduced pellets was 48.5 square meters per gram.and their average crushing strength of the unreduced pellets was 4.8pounds. On the basis of the propylene charge, the organic nitrogencompounds produced, calculated as propionitriie was 10.5% by.

- thereby seriously impaired.

The surface area values given herein are based on the amount of stearicacid adsorbed by the material from a benzene eral assumption that theentire surface of the material is covered with a mono-molecular layer ofstearic acid in such a state of orientation and packing that eachmolecule occupies about 20A, as has been previously. discussed rathergenerally in the literature. Briefly, the apparatus employed consists ofa catalyst-adsorption tube having an upper and lower compartment andadapted to be evacuated and heated. A sample of the material,

On the same basis, the total nitrogen 1 solution and the gen- 1nsuspension on a carrier tubeuhtil the solid material is well coveredw'iththe solution. "The-lower portion of thetubeis' then sep'a'ratedfrom the upper portion, tightly sealedand rotated end-'over-end at arate of about R; P. M. for approximately Thours. It is'then'allowedto'settle for 15 hours or more until the supernatant liquid is clear.Samples of the supernatant liquid are thenremoved and their stearic acidconcentration compared with the concentration of the original solution.From these values the amount of stearic acid adsorbed by the solidmaterial and the surface area of the solid material are then calculated.The term "porosity fined generally as the parent volume of thecompartment oi the ied by the solid matter, The porosity values ivenwere determined by the differential displacement in water and mercury,the displacements of the respective liquids being measured after thecareful elimination of dissolved or occluded gases from the water andmercury and the evacuation of the material, the porosity of which was tobe measured.

- The catalysts of my present invention are with advantage used as afixed bed through which an admixture of the reactants are passed or withwhich the reactants are otherwise brought into contact. In the processof this type I prefer to use the catalyst in a pelleted form. However, mimproved catalysts are also applicable to amination processes of thetype in which the catalyst inv finely-divided form is passedcontinuously to the reaction zone in suspension Mom of the reactants ora mixture thereof.

In either type of operation it eventually becomes necessary toregenerate the catalyst to restore its selective amination activitywhich gradually diminishes with continued use. This regeneration mayreadil be eifected by periodically subjecting the degenerated catalystto an atmosphere of hydrogen at a temperature of about 650-750 F. and atatmospheric pressure for about 12 to 50 hours.

I claim:

l. A catalytic mass selectively promoting amination of olefins in thepresence of ammonia comprising a metal of the class consisting of cobaltnickel in suspension on a carrier of acidtreated bentonite whichsubsequent to the acidtreatment but prior to the deposition of the metalthereon has been subjected to a temperature of about 1400 F. to 1600 F.for a period of about 6 to 8 hours.

2. A catalytic mass selectively promoting amination of olefins in thepresence of ammonia comprising about 40%-50% by weight of a metal of theclass consisting of cobalt and nickel in suspension on a carrier ofacid-treated bentonite which subsequent to the acid-treatment but priorsubjected to a temperature of about 1400 F. to 1600 F. for a period ofabout 6 to 8 hours.

3. A-catalytic mass selectively promoting amination of olefins in thepresence of ammonia comprising about'40%-50% by weight of cobalt I ofacid-treated bentonite which subsequent to the acid-treatment but priorto the deposition of the metal thereon has been subjected to atemperature of about 1400" F'. to 1600 F. for a period of about 6 to 8hours.

4. A catalytic mass selectively promoting amination of olefins in thepresence of ammonia comprising about 40%-50% by weight 0! nickel insuspension on a carrier of acid-treated bentonite which subsequent tothe acid-treatment but prior to the deposition of the metal thereon hasbeen subjected to a temperature of about 1400 F. to 1600" F. for aperiod of about 6 to 8 hours.

5. The method of producing a catalytic mass selectively promotingamination of an olefin in the presence of ammonia which comprisesheating an acid-treated bentonite to a temperature 5 of about 1400* F.to 1600 F. for a period of about 6 to 8 hours, precipitating thereon acompound of a metal of the class consisting of cobalt and nickel capableupon calcination of forming the oxide of the metal, calcining the massto convert the metal compound to the metal oxide and reducing the oxideby subjecting the mass to an atmosphere of hydrogen at an elevatedtemperature.

JOHN W. 'I'EIER.

